Appropriateness and Quality of Composite Endpoint Use and Reporting in Spine Surgery: A Systematic Review.

BACKGROUND: A composite endpoint (CEP) is a measure comprising 2 or more separate component outcomes. The use of these constructs is increasing. We sought to conduct a systematic review on the usage, quality of reporting, and appropriate use of CEPs in spine surgery research. METHODS: A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Articles reporting randomized controlled trials of a spine surgery intervention using a CEP as a primary outcome were included. We assessed the quality of CEP reporting, appropriateness of CEP use, and correspondence between CEP treatment effect and component outcome treatment effect in the included trials. RESULTS: Of 2,321 initial titles, 43 citations were included for analysis, which reported on 20 unique trials. All trials reported the CEP construct well. In 85% of trials, the CEP design was driven by US Food and Drug Administration guidance. In the majority of trials, the reporting of CEP results did not adhere to published recommendations: 43% of tests that reported statistically significant results on component outcomes were not statistically significant when adjusted for multiple testing. 67% of trials did not meet appropriateness criteria for CEP use. In addition, CEP treatment effect tended to be 6% higher than the median treatment effect for component outcomes. CONCLUSION: Given that CEP analysis was not appropriate for the majority of spine surgery trials and the inherent challenges in the reporting and interpretation of CEP analysis, CEP use should not be mandated by regulatory bodies in spine surgery trials. LEVEL OF EVIDENCE: Level I. See Instructions for Authors for a complete description of levels of evidence.

Immobilization protocols for the treatment of cervical spine fracture: a scoping review.

BACKGROUND: Current protocols on cervical immobilization postcervical spine fracture are widely accepted in the acute rehabilitation of older adults, however consensus on its overall effectiveness remains lacking. PURPOSE: Summarize information from original studies on available cervical immobilization protocols following a cervical fracture and to answer the questions; Which types of study designs have been used to assess the effectiveness of these protocols? What are the currently reported cervical immobilization protocols following cervical fracture in adults? What is the effectiveness of these protocols? What adverse events are associated with these protocols? STUDY DESIGN: Scoping review was performed. PATIENT SAMPLE: Searches were performed on the following online databases from inception to February 23, 2023: EMBASE, MEDLINE, CINAHL, and CENTRAL. Databases were searched for articles pertaining to collar use post cervical spine fracture. OUTCOME MEASURES: Effectiveness of the cervical fracture immobilization protocols was the primary outcome, examined by various measures including union rates and disability indexes. METHODS: 4 databases were searched; EMBASE, MEDLINE, Cumulative Index of Nursing and Allied Health Literature (CINAHL), and Cochrane Central Register of Controlled Trials (CENTRAL) beginning on February 23, 2023, where 5,127 studies were yielded and 32 were extracted based on studies of adults (≥18 years) with a diagnosis of a cervical fracture (C0-C7) managed with a rigid external orthosis to prevent instability and surgery (collar, or cervicothoracic orthosis). Risk of bias was assessed using the guidelines set out by the Joanna Briggs Institute. RESULTS: This scoping review yielded low-level prospective (18%) and retrospective (69%) cohort studies, case-control studies (3%), and case series (6%) from 1987 to 2022, patient age ranged from 14 to 104 years. Findings were difficult to summarize based on the lack of randomized controlled trials, leading to no clear conclusions drawn on the presence of standardized cervical immobilization protocols with no information on the duration of treatment or transition in care. Most included articles were retrospective cohort studies of poor to moderate quality, which have significant risk of bias for intervention questions. The effectiveness of these protocols remains unclear as most studies evaluated heterogeneous outcomes and did not present between-group differences. Mortality, musculoskeletal (MSK) complications, and delayed surgery were common adverse events associated with cervical collar use. CONCLUSION: This scoping review highlights the need for higher levels of evidence as there is currently no standardized immobilization protocol for cervical spine fractures as a primary treatment, the effectiveness of cervical immobilization protocols is unclear, and mortality, MSK complications, and delayed surgery are common adverse events. No sources of funding were used for this scoping review.

Traumatic penetrating head injury by crossbow projectiles: A case report and literature review.

Background: Low-energy penetrating head injuries caused by arrows are relatively uncommon. The objective of this report is to describe a case presentation and management of self-inflicted intracranial injury using a crossbow and to provide a relevant literature review. Case Report: A 31-year-old man with a previous psychiatric history sustained a self-inflicted injury using a crossbow that he bought from a department store. The patient arrived neurologically intact at the hospital, fully awake and oriented. He was not able to verbalize due to immobilization of the jaw as well as fixation of his tongue to his hard palate secondary to the position of the arrow. The trajectory of the object showed an entry point at the floor of the oral cavity and an exit through the calvarium just off the midline. The oral and nasal cavity, along with the palate and, the skull base of the anterior cranial fossa, and the left frontal lobe, were all breached. No vascular injury was identified clinically or in imaging. The arrow was surgically removed in the operating room after establishing an elective surgical airway. The floor of the mouth, tongue, and palate was repaired next. A planned delayed cerebrospinal fluid leak repair was performed. The patient made a substantial recovery and was discharged home in good functional status. A systematic literature search was done using Medline for cases with intracranial injuries related to crossbows to review and appraise the available literature. Conclusion: A thorough assessment in a multidisciplinary trauma center and the availability of a subspecialty care team, including neurosurgery and otolaryngology, are paramount in such cases. The vascular imaging should be done before and after any planned surgical intervention. Emergent and elective surgical airway management should be considered and made available throughout the stabilization and care of the acute injury. Surgical management should be planned to remove the object with adequate exposure to facilitate visualization, removal, and the possible need for further intervention, including anticipating aerodigestive and vascular injuries on removal. Finally, access to weapons and the relation to psychiatric illness should not be overlooked, as many reported cases are self-harming in nature.

The Development And Applications Of Augmented And Virtual Reality Technology In Spine Surgery Training: A Systematic Review.

BACKGROUND: The COVID-19 pandemic has accelerated the growing global interest in the role of augmented and virtual reality in surgical training. While this technology grows at a rapid rate, its efficacy remains unclear. To that end, we offer a systematic review of the literature summarizing the role of virtual and augmented reality on spine surgery training. METHODS: A systematic review of the literature was conducted on May 13th, 2022. PubMed, Web of Science, Medline, and Embase were reviewed for relevant studies. Studies from both orthopedic and neurosurgical spine programs were considered. There were no restrictions placed on the type of study, virtual/augmented reality modality, nor type of procedure. Qualitative data analysis was performed, and all studies were assigned a Medical Education Research Study Quality Instrument (MERSQI) score. RESULTS: The initial review identified 6752 studies, of which 16 were deemed relevant and included in the final review, examining a total of nine unique augmented/virtual reality systems. These studies had a moderate methodological quality with a MERSQI score of 12.1 + 1.8; most studies were conducted at single-center institutions, and unclear response rates. Statistical pooling of the data was limited by the heterogeneity of the study designs. CONCLUSION: This review examined the applications of augmented and virtual reality systems for training residents in various spine procedures. As this technology continues to advance, higher-quality, multi-center, and long-term studies are required to further the adaptation of VR/AR technologies in spine surgery training programs.

Natural history of degenerative cervical myelopathy: a meta-analysis and neurologic deterioration survival curve synthesis.

BACKGROUND CONTEXT: Cervical spine surgery is rapidly increasing, and our knowledge of the natural history of degenerative cervical myelopathy (DCM) is limited. PURPOSE: To synthesize accurate time-based estimates of meaningful neurologic decline in patients with DCM managed conservatively and to provide formulae to help communicate survivorship estimates to patients. STUDY DESIGN: Systematic review and meta-analysis. METHODS: A systematic review and meta-analysis was conducted using Cochrane and PRISMA guidelines. A librarian-assisted search strategy using multiple databases with broad search terms and validated filter functions was used. All articles were reviewed in duplicate. RESULTS: A total of 9570 studies were captured in the initial search, which after deletion of duplicates and manual review of abstracts and full texts revealed 6 studies for analyses. All studies were prospective cohorts or randomized controlled trials. The pooled survival estimates for neurologic stability (95% CrI) for mild DCM patients are: 91% (83%-97%) at one year; 85% (72%-94%) at 2 years; 84% (70%-94%) at 3 years; 75% (54%-90%) at 5 years; 66% (40%-86%) at 15 years; and 65% (39%-86%) at 20 years. The pooled survival estimates for neurologic stability (95% CrI) for moderate/severe DCM patients are: 83% (76%-89%) at 1 year; 72% (62%-81%) at 2 years; 71% (60%-80%) at 3 years; 55% (41%-68%) at 5 years; 44% (27%-59%) at 15 years; and 43% (25%-58%) at 20 years. CONCLUSIONS: This is the first quantitative synthesis of the totality of published data on DCM natural history. Our review confirms a slow decline in neurologic function. We developed formulae which can be easily used by surgeons to communicate to patients their risk of neurologic deterioration. These formulae can be used to facilitate the shared decision-making process.

Graft subsidence and reoperation after lateral lumbar interbody fusion: a propensity score-matched and cost analysis of polyetheretherketone versus 3D-printed porous titanium interbodies.

OBJECTIVE: Lumbar interbody cage subsidence has a multifactorial etiology. Cage material, although well studied after transforaminal lumbar interbody fusion, has not been investigated as a contributing factor to subsidence after lateral lumbar interbody fusion (LLIF). In this study the authors compared rates of subsidence and reoperation after LLIF between polyetheretherketone (PEEK) and 3D-printed porous titanium (pTi) in an institutional propensity score-matched and cost analysis. METHODS: This is a retrospective observational cohort analysis of adult patients who underwent LLIF with pTi versus PEEK between 2016 and 2020. Demographic, clinical, and radiographic characteristics were collected. Propensity scores were calculated and 1:1 matching without replacement of surgically treated levels was performed. The primary outcome of interest was subsidence. The Marchi subsidence grade was determined at the time of last follow-up. Chi-square or Fisher's exact tests were used to compare subsidence and reoperation rates between lumbar levels treated with PEEK versus pTi. Modeling and cost analysis were performed using TreeAge Pro Healthcare. RESULTS: The authors identified a total of 192 patients; 137 underwent LLIF with PEEK (212 levels) and 55 had LLIF with pTi (97 levels). After propensity score matching, a total of 97 lumbar levels remained in each treatment group. After matching, there were no statistically significant differences between groups in baseline characteristics. Levels treated with pTi were significantly less likely to exhibit subsidence (any grade) compared to those treated with PEEK (8% vs 27%, p = 0.001). Five (5.2%) levels treated with PEEK required reoperation for subsidence, but only 1 (1.0%) level treated with pTi required reoperation for subsidence (p = 0.12). Given subsidence and revision rates experienced in the cohorts in this study, the pTi interbody device is economically superior to PEEK in a single-level LLIF as long as its cost is at least $1185.94 lower than that of PEEK. CONCLUSIONS: The pTi interbody device was associated with less subsidence, but statistically similar revision rates after LLIF. pTi is potentially a superior economic choice at this study's reported revision rate.

Long-Term Survivorship of Cervical Spine Procedures; A Survivorship Meta-Analysis and Meta-Regression.

STUDY DESIGN: Systematic Review. OBJECTIVES: To conduct a meta-analysis on the survivorship of commonly performed cervical spine procedures to develop survival function curves for (i) second surgery at any cervical level, and (ii) adjacent level surgery. METHODS: A systematic review of was conducted following PRISMA guidelines. Articles with cohorts of greater than 20 patients followed for a minimum of 36 months and with available survival data were included. Procedures included were anterior cervical discectomy and fusion (ACDF), cervical disc arthroplasty (ADR), laminoplasty (LAMP), and posterior laminectomy and fusion (PDIF). Reconstructed individual patient data were pooled across studies using parametric Bayesian survival meta-regression. RESULTS: Of 1829 initial titles, 16 citations were included for analysis. 73 811 patients were included in the second surgery analysis and 2858 patients in the adjacent level surgery analysis. We fit a Log normal accelerated failure time model to the second surgery data and a Gompertz proportional hazards model to the adjacent level surgery data. Relative to ACDF, the risk of second surgery was higher with ADR and PDIF with acceleration factors 1.73 (95% CrI: 1.04, 2.80) and 1.35 (95% CrI: 1.25, 1.46) respectively. Relative to ACDF, the risk of second surgery was lower with LAMP with deceleration factor .06 (95% CrI: .05, .07). ADR decreased the risk of adjacent level surgery with hazard ratio .43 (95% CrI: .33, .55). CONCLUSIONS: In cases of clinical equipoise between fusion procedures, our analysis suggests superior survivorship with anterior procedures. For all procedures, laminoplasty demonstrated superior survivorship.

Subsidence after lateral lumbar interbody fusion using a 3D-printed porous titanium interbody cage: single-institution case series.

OBJECTIVE: Cage subsidence is a well-known phenomenon after lateral lumbar interbody fusion (LLIF), occurring in 10%-20% of cases. A 3D-printed porous titanium (pTi) cage has a stiffness that mimics the modulus of elasticity of native vertebrae, which reduces stress at the bone-hardware interface, lowering the risk of subsidence. In this study, the authors evaluated their institutional rate of subsidence and resultant reoperation in patients who underwent LLIF using a 3D-printed pTi interbody cage. METHODS: This is a retrospective case series of consecutive adult patients who underwent LLIF using pTi cages from 2018 to 2020. Demographic and clinical characteristics including age, sex, bone mineral density, smoking status, diabetes, steroid use, number of fusion levels, posterior instrumentation, and graft size were collected. The Marchi subsidence grade was determined at the time of last follow-up. Outcome measures of interest were subsidence and resultant reoperation. Univariable logistic regression analysis was performed to assess the extent to which clinical and operative characteristics were associated with Marchi grade I-III subsidence. Significance was assessed at p < 0.05. RESULTS: Fifty-five patients (38 with degenerative disc disease and 17 with adult spinal deformity) were treated with 97 pTi interbody cages with a mean follow-up of 18 months. The mean age was 63.6 ± 10.1 years, 60% of patients were female, and 36% of patients had osteopenia or osteoporosis. Patients most commonly underwent single-level LLIF (58.2%). Sixteen patients (29.1%) had posterior instrumentation. The subsidence grade distribution was as follows: 89 (92%) grade 0, 5 (5%) grade I, 2 (2%) grade II, and 1 (1%) grade III. No patients who were active or prior smokers and no patients with posterior instrumentation experienced graft subsidence. No clinical or operative characteristics were significantly associated with graft subsidence. One patient (1.8%) required reoperation because of subsidence. CONCLUSIONS: In this institutional case series, subsidence of pTi intervertebral cages after LLIF occurred in 8% of operated levels, 3% of which were grade II or III. Only 1 patient required reoperation. These reported rates are lower than those reported for polyetheretherketone implants. Further studies are necessary to compare the impact of these cage materials on subsidence after LLIF.

Machine-vision image guided C4-C5 unilateral cervical pedicle screw insertion: case report and review of literature.

Computer-assistance for pedicle screw insertion is becoming increasingly common. As in the case presented below, image guided neuronavigation can be used to improve the accuracy and safety of subaxial cervical pedicle screw placement, given their increased difficulty of cannulation relative to the larger pedicles in the thoracolumbar spine. A 49-year-old man presented with a traumatic sagittal split fracture of C4 (AO Classification type A4) and a left lateral mass fracture of C5 (AO Classification type F1) with anterior depression and 50% height loss. MRI revealed evidence of strain of the interspinous/supraspinous ligaments (AO Classification type B2), as well as fluid within the left C4-C5 facet joint. Along with these fractures, the young patient had Klippel-Feil syndrome with autofusion of the C2-3 posterior elements, and a left vertebral artery dissection. He had neck pain but was otherwise neurologically intact. The patient underwent machine-vision image guided C4-C5 unilateral pedicle screw insertion connected by a fixation rod for stabilization and bone graft to augment the instrumented fusion with good outcome. The use of machine vision spinal navigation was able to provide accurate and precise placement of pedicle screws without significantly increasing surgical time. This method has the potential to allow for the safe and accurate insertion of cervical pedicle screws and to reduce the rate of pedicle breach which could avoid significant neurovascular injury.

Computed Tomography Hounsfield Units as a Predictor of Reoperation and Graft Subsidence After Standalone and Multilevel Lateral Lumbar Interbody Fusion.

BACKGROUND: Standalone single and multilevel lateral lumbar interbody fusion (LLIF) have been increasingly applied to treat degenerative spinal conditions in a less invasive fashion. Graft subsidence following LLIF is a known complication and has been associated with poor bone mineral density (BMD). Previous research has demonstrated the utility of computed tomography (CT) Hounsfield units (HUs) as a surrogate for BMD. In the present study, we investigated the relationship between the CT HUs and subsidence and reoperation after standalone and multilevel LLIF. METHODS: A prospectively maintained single-institution database was retrospectively reviewed for LLIF patients from 2017 to 2020, including single and multilevel standalone cases with and without supplemental posterior fixation. Data on demographics, graft parameters, BMD determined by dual-energy x-ray absorptiometry, preoperative mean segmental CT HUs, and postoperative subsidence and reoperation were collected. We used 36-in. standing radiographs to measure the preoperative global sagittal alignment and disc height and subsidence at last follow-up. Subsidence was classified using the Marchi grading system corresponding to disc height loss: grade 0, 0%-24%; grade I, 25%-49%; grade II, 50%-74%; and grade III, 75%-100%. RESULTS: A total of 89 LLIF patients had met the study criteria, with a mean follow-up of 19.9 ± 13.9 months. Of the 54 patients who had undergone single-level LLIF, the mean segmental HUs were 152.0 ± 8.7 for 39 patients with grade 0 subsidence, 136.7 ± 10.4 for 9 with grade I subsidence, 133.9 ± 23.1 for 3 with grade II subsidence, and 119.9 ± 30.9 for 3 with grade III subsidence (P = 0.032). Of the 96 instrumented levels in the 35 patients who had undergone multilevel LLIF, 85, 9, 1, and 1 level had had grade 0, grade I, grade II, and grade III subsidence, with no differences in the HU levels. On multivariate logistic regression, increased CT HU levels were independently associated with a decreased risk of reoperation after both single-level and multilevel LLIF (odds ratio, 0.98; 95% confidence interval, 0.97-0.99; P = 0.044; and odds ratio, 0.97; 95% confidence interval, 0.94-0.99; P = 0.017, respectively). Overall, the BMD determined using dual-energy x-ray absorptiometry was not associated with graft subsidence or reoperation. Using a receiver operating characteristic curve to separate the patients who had and had not required reoperation, the threshold HU level determined for single-level and multilevel LLIF was 131.4 (sensitivity, 0.62; specificity 0.65) and 131.0 (sensitivity, 0.67; specificity, 0.63), respectively. CONCLUSIONS: Lower CT HUs were independently associated with an increased risk of graft subsidence after single-level LLIF. In addition, lower CT HUs significantly increased the risk of reoperation after both single and multilevel LLIF with a critical threshold of 131 HUs. The determination of the preoperative CT HUs might provide a more robust gauge of local bone quality and the likelihood of graft subsidence requiring reoperation following LLIF than overall BMD.

Machine vision augmented reality for pedicle screw insertion during spine surgery.

Implementing pedicle safe zones with augmented reality has the potential to improve operating room workflow during pedicle screw insertion. These safe zones will allow for image guidance when tracked instruments are unavailable. Using the correct screw trajectory as a reference angle for a successful screw insertion, we will determine the angles which lead to medial, lateral, superior and inferior breaches. These breaches serve as the boundaries of the safe zones. Measuring safe zones from the view of the surgical site and comparing to the radiological view will further understand the visual relationship between the radiological scans and the surgical site. Safe zones were measured on a spine phantom and were then replicated on patients. It was found that the largest causes for variance was between each of the camera views and the radiological views. The differences between the left and right cameras were insignificant. Overall, the camera angles appeared to be larger than the radiological angles. The magnification effect found in the surgical site result in an increased level of angle sensitivity for pedicle screw insertion techniques. By designing a virtual road map on top of the surgical site directly using tracked tools, the magnification effect is already taken into consideration during surgery. Future initiatives include the use of an augmented reality headset.

An augmented reality system characterization of placement accuracy in neurosurgery.

Computer assisted navigation (CAN) is a technology which has been available for commercial use in operating rooms for quite some time now. CAN relies on the information presented in patient imaging (usually CT or MRI images) and the surgical site. The method for registration between these two sets of data is crucial for safe image guided navigation during surgery. Although the existing technologies are extremely accurate, they still pose problems in the operating. Motivation for this study is to explore the possibility of using augmented reality (AR) to improve ease of use for surgical navigation and provide a system which complements the existing operating room workflow. As with all commercially available surgical navigation systems, registration accuracy is of utmost important to maintain patient safety. In this paper, we propose a novel method to quantify registration accuracy for augmented reality (AR) devices in neurosurgery.

Quantification of computational geometric congruence in surface-based registration for spinal intra-operative three-dimensional navigation.

BACKGROUND CONTEXT: Computer-assisted navigation (CAN) may guide spinal instrumentation, and requires alignment of patient anatomy to imaging. Iterative closest-point (ICP) algorithms register anatomical and imaging surface datasets, which may fail in the presence of geometric symmetry (congruence), leading to failed registration or inaccurate navigation. Here we computationally quantify geometric congruence in posterior spinal exposures, and identify predictors of potential navigation inaccuracy. METHODS: Midline posterior exposures were performed from C1-S1 in four human cadavers. An optically-based CAN generated surface maps of the posterior elements at each level. Maps were reconstructed to include bilateral hemilamina, or unilateral hemilamina with/without the base of the spinous process. Maps were fitted to symmetrical geometries (cylindrical/spherical/planar) using computational modelling, and the degree of model fit quantified based on the ratio of model inliers to total points. Geometric congruence was subsequently assessed clinically in 11 patients undergoing midline exposures in the cervical/thoracic/lumbar spine for posterior instrumented fusion. RESULTS: In cadaveric testing, increased cylindrical/spherical/planar symmetry was seen in the high-cervical and subaxial cervical spine relative to the thoracolumbar spine (p<0.001). Extension of unilateral exposures to include the ipsilateral base of the spinous process decreased symmetry independent of spinal level (p<0.001). In clinical testing, increased cylindrical/spherical/planar symmetry was seen in the subaxial cervical relative to the thoracolumbar spine (p<0.001), and in the thoracic relative to the lumbar spine (p<0.001). Symmetry in unilateral exposures was decreased by 20% with inclusion of the ipsilateral base of the spinous process. CONCLUSIONS: Geometric congruence is most evident at C1 and the subaxial cervical spine, warranting greater vigilance in navigation accuracy verification. At all levels, inclusion of the base of the spinous process in unilateral registration decreases the likelihood of geometric symmetry and navigation error. This work is important to allow the extension of line-of-sight based registration techniques to minimally-invasive unilateral approaches.

Intraoperative Error Propagation in 3-Dimensional Spinal Navigation From Nonsegmental Registration: A Prospective Cadaveric and Clinical Study.

STUDY DESIGN: Prospective pre-clinical and clinical cohort study. OBJECTIVES: Current spinal navigation systems rely on a dynamic reference frame (DRF) for image-to-patient registration and tool tracking. Working distant to a DRF may generate inaccuracy. Here we quantitate predictors of navigation error as a function of distance from the registered vertebral level, and from intersegmental mobility due to surgical manipulation and patient respiration. METHODS: Navigation errors from working distant to the registered level, and from surgical manipulation, were quantified in 4 human cadavers. The 3-dimensional (3D) position of a tracked tool tip at 0 to 5 levels from the DRF, and during targeting of pedicle screw tracts, was captured in real-time by an optical navigation system. Respiration-induced vertebral motion was quantified from 10 clinical cases of open posterior instrumentation. The 3D position of a custom spinous-process clamp was tracked over 12 respiratory cycles. RESULTS: An increase in mean 3D navigation error of ≥2 mm was observed at ≥2 levels from the DRF in the cervical and lumbar spine. Mean ± SD displacement due to surgical manipulation was 1.55 ± 1.13 mm in 3D across all levels, ≥2 mm in 17.4%, 19.2%, and 38.5% of levels in the cervical, thoracic, and lumbar spine, respectively. Mean ± SD respiration-induced 3D motion was 1.96 ± 1.32 mm, greatest in the lower thoracic spine (P < .001). Tidal volume and positive end-expiratory pressure correlated positively with increased vertebral displacement. CONCLUSIONS: Vertebral motion is unaccounted for during image-guided surgery when performed at levels distant from the DRF. Navigating instrumentation within 2 levels of the DRF likely minimizes the risk of navigation error.

Optical Topographic Imaging for Spinal Intraoperative 3-Dimensional Navigation in the Cervical Spine: Initial Preclinical and Clinical Feasibility.

OF BACKGROUND DATA: Computer-assisted 3-dimensional navigation may guide spinal instrumentation. Optical topographic imaging (OTI) is a novel navigation technique offering comparable accuracy and significantly faster registration workflow relative to current navigation systems. It has previously been validated in open posterior thoracolumbar exposures. OBJECTIVE: To validate the utility and accuracy of OTI in the cervical spine. STUDY DESIGN: This is a prospective preclinical cadaveric and clinical cohort study. METHODS: Standard midline open posterior cervical exposures were performed, with segmental OTI registration at each vertebral level. In cadaveric testing, OTI navigation guidance was used to track a drill guide for cannulating screw tracts in the lateral mass at C1, pars at C2, lateral mass at C3-6, and pedicle at C7. In clinical testing, translaminar screws at C2 were also analyzed in addition. Planned navigation trajectories were compared with screw positions on postoperative computed tomographic imaging, and quantitative navigation accuracies, in the form of absolute translational and angular deviations, were computed. RESULTS: In cadaveric testing (mean±SD) axial and sagittal translational navigation errors were (1.66±1.18 mm) and (2.08±2.21 mm), whereas axial and sagittal angular errors were (4.11±3.79 degrees) and (6.96±5.40 degrees), respectively.In clinical validation (mean±SD) axial and sagittal translational errors were (1.92±1.37 mm) and (1.27±0.97 mm), whereas axial and sagittal angular errors were (3.68±2.59 degrees) and (3.47±2.93 degrees), respectively. These results are comparable to those achieved with OTI in open thoracolumbar approaches, as well as using current spinal neuronavigation systems in similar applications. There was no radiographic facet, canal or foraminal violations, nor any neurovascular complications. CONCLUSIONS: OTI is a novel navigation technique allowing efficient initial and repeat registration. Accuracy even in the more mobile cervical spine is comparable to current spinal neuronavigation systems.

Optical Topographic Imaging for Spinal Intraoperative Three-Dimensional Navigation in Mini-Open Approaches: A Prospective Cohort Study of Initial Preclinical and Clinical Feasibility.

OBJECTIVE: Computer-assisted three-dimensional navigation often guides spinal instrumentation. Optical topographic imaging (OTI) offers comparable accuracy and significantly faster registration relative to current navigation systems in open posterior thoracolumbar exposures. We validate the usefulness and accuracy of OTI in minimally invasive spinal approaches. METHODS: Mini-open midline posterior exposures were performed in 4 human cadavers. Square exposures of 25, 30, 35, and 40 mm were registered to preoperative computed tomography imaging. Screw tracts were fashioned using a tracked awl and probe with instrumentation placed. Navigation data were compared with screw positions on postoperative computed tomography imaging, and absolute translational and angular deviations were computed. In vivo validation was performed in 8 patients, with mini-open thoracolumbar exposures and percutaneous placement of navigated instrumentation. Navigated instrumentation was performed in the previously described manner. RESULTS: For 37 cadaveric screws, absolute translational errors were (1.79 ± 1.43 mm) and (1.81 ± 1.51 mm) in the axial and sagittal planes, respectively. Absolute angular deviations were (3.81 ± 2.91°) and (3.45 ± 2.82°), respectively (mean ± standard deviation). The number of surface points registered by the navigation system, but not exposure size, correlated positively with the likelihood of successful registration (odds ratio, 1.02; 95% confidence interval, 1.009-1.024; P < 0.001). Fifty-five in vivo thoracolumbar pedicle screws were analyzed. Overall (mean ± standard deviation) axial and sagittal translational errors were (1.79 ± 1.41 mm) and (2.68 ± 2.26 mm), respectively. Axial and sagittal angular errors were (3.63° ± 2.92°) and (4.65° ± 3.36°), respectively. There were no radiographic breaches >2 mm or any neurovascular complications. CONCLUSIONS: OTI is a novel navigation technique previously validated for open posterior exposures and in this study has comparable accuracy for mini-open minimally invasive surgery exposures. The likelihood of successful registration is affected more by the geometry of the exposure than by its size.

Utilization of Spinal Intra-operative Three-dimensional Navigation by Canadian Surgeons and Trainees: A Population-based Time Trend Study.

BACKGROUND: Computer-assisted navigation (CAN) improves the accuracy of spinal instrumentation in vertebral fractures and degenerative spine disease; however, it is not widely adopted because of lack of training, high capital costs, workflow hindrances, and accuracy concerns. We characterize shifts in the use of spinal CAN over time and across disciplines in a single-payer health system, and assess the impact of intra-operative CAN on trainee proficiency across Canada. METHODS: A prospectively maintained Ontario database of patients undergoing spinal instrumentation from 2005 to 2014 was reviewed retrospectively. Data were collected on treated pathology, spine region, surgical approach, institution type, and surgeon specialty. Trainee proficiency with CAN was assessed using an electronic questionnaire distributed across 15 Canadian orthopedic surgical and neurosurgical programs. RESULTS: In our provincial cohort, 16.8% of instrumented fusions were CAN-guided. Navigation was used more frequently in academic institutions (15.9% vs. 12.3%, p<0.001) and by neurosurgeons than orthopedic surgeons (21.0% vs. 12.4%, p<0.001). Of residents and fellows 34.1% were fully comfortable using spinal CAN, greater for neurosurgical than orthopedic surgical trainees (48.1% vs. 11.8%, p=0.008). The use of CAN increased self-reported proficiency in thoracic instrumentation for all trainees by 11.0% (p=0.036), and in atlantoaxial instrumentation for orthopedic trainees by 18.0% (p=0.014). CONCLUSIONS: Spinal CAN is used most frequently by neurosurgeons and in academic centers. Most spine surgical trainees are not fully comfortable with the use of CAN, but report an increase in technical comfort with CAN guidance particularly for thoracic instrumentation. Increased education in spinal CAN for trainees, particularly at the fellowship stage and, specifically, for orthopedic surgery, may improve adoption.

CONTEXTE: La chirurgie assistée par ordinateur (CAO) permet d'améliorer la précision de l'exploration instrumentale employée dans le cas de fractures vertébrales et de maladies dégénératives de la colonne vertébrale. Cela dit, elle n'a pas encore été adoptée à grande échelle en raison d'un manque de formation, de coûts d'immobilisation considérables, d'obstacles liés à l'organisation du travail et de doutes quant à son exactitude. C'est dans cette perspective que nous voulons décrire, parmi divers champs de pratique, les transformations se rapportant au fil du temps à l'utilisation de la CAO de la colonne vertébral dans le cadre d'un régime de santé universel à payeur unique. Qui plus est, nous voulons aussi évaluer l'impact de la CAO en ce qui a trait aux compétences des stagiaires partout au Canada. MÉTHODES: Pour ce faire, nous avons passé en revue de façon rétrospective une base de données tenue à jour prospectivement au sujet de patients ontariens ayant été soumis de 2005 à 2014 à une exploration instrumentale de la colonne vertébrale. Les données obtenues portaient sur le type de pathologie traitée, sur la région de la colonne vertébrale visée, sur l'approche chirurgicale privilégiée, sur le type d'établissement et sur la spécialité du chirurgien ayant intervenu. Les compétences des stagiaires en matière de CAO ont également été évaluées à l'aide d'un questionnaire en ligne diffusé au sein de 15 programmes canadiens de chirurgie orthopédique et de neurochirurgie. RÉSULTATS: En tout, 16,8 % des fusions instrumentées réalisées au sein de notre cohorte ontarienne l'ont été à l'aide de la technique de la CAO. Cette dernière a été utilisée plus fréquemment dans des établissements d'enseignement universitaire (15,9 % par opposition à 12,3 % pour les autres; p<0,001) mais aussi plus souvent par des neurochirurgiens (21,0 % par opposition à 12,4 % par des chirurgiens orthopédiques; p<0,001). En outre, 34,1 % des résidents et des médecins suivant une formation complémentaire étaient parfaitement à l'aise dans l'utilisation de la CAO de la colonne vertébrale (48,1 % de ceux se spécialisant en neurochirurgie par opposition à 11,8 % de ceux se spécialisant en chirurgie orthopédique; p = 0,008). L'utilisation de la CAO a par ailleurs entraîné une augmentation, auto-déclarée, de 11,0 % de l'aptitude à faire usage de l'exploration instrumentale thoracique chez tous les stagiaires (p = 0,036); dans le cas de l'exploration instrumentale atlanto-axiale, cette augmentation a été de 18,0 % (p = 0,014) chez les stagiaires en chirurgie orthopédique. CONCLUSIONS: La CAO de la colonne vertébrale est employée le plus souvent par les neurochirurgiens dans des établissements d'enseignement universitaire. La plupart des stagiaires en chirurgie de la colonne vertébrale ne sont pas entièrement à l'aise en ce qui concerne l'utilisation de la CAO. Toutefois, ils ont signalé une augmentation de leur aisance à utiliser la CAO et à bénéficier de son assistance, en particulier dans des cas d'exploration instrumentale thoracique. En somme, une plus ample formation en matière de CAO de la colonne vertébrale offerte aux stagiaires, particulièrement à ceux suivant une formation complémentaire et dans le champ de la chirurgie orthopédique, pourrait favoriser son adoption.

High Speed, High Density Intraoperative 3D Optical Topographical Imaging with Efficient Registration to MRI and CT for Craniospinal Surgical Navigation.

Intraoperative image-guided surgical navigation for craniospinal procedures has significantly improved accuracy by providing an avenue for the surgeon to visualize underlying internal structures corresponding to the exposed surface anatomy. Despite the obvious benefits of surgical navigation, surgeon adoption remains relatively low due to long setup and registration times, steep learning curves, and workflow disruptions. We introduce an experimental navigation system utilizing optical topographical imaging (OTI) to acquire the 3D surface anatomy of the surgical cavity, enabling visualization of internal structures relative to exposed surface anatomy from registered preoperative images. Our OTI approach includes near instantaneous and accurate optical measurement of >250,000 surface points, computed at >52,000 points-per-second for considerably faster patient registration than commercially available benchmark systems without compromising spatial accuracy. Our experience of 171 human craniospinal surgical procedures, demonstrated significant workflow improvement (41 s vs. 258 s and 794 s, p < 0.05) relative to benchmark navigation systems without compromising surgical accuracy. Our advancements provide the cornerstone for widespread adoption of image guidance technologies for faster and safer surgeries without intraoperative CT or MRI scans. This work represents a major workflow improvement for navigated craniospinal procedures with possible extension to other image-guided applications.

High-Frequency Micro-Ultrasound Imaging and Optical Topographic Imaging for Spinal Surgery: Initial Experiences.

High frequency micro-ultrasound (µUS) transducers with central frequencies up to 50 MHz facilitate dynamic visualization of patient anatomy with minimal disruption of the surgical work flow. Micro-ultrasound improves spatial resolution over conventional ultrasound imaging from millimeter to micrometer, but compromises depth penetration. This trade-off is sufficient during an open surgery in which the bone is removed and theultrasound probe can be placed into the surgical cavity. By fusing µUS with pre-operative imaging and tracking the ultrasound probe intra-operatively using our optical topographic imaging technology, we can provide dynamic feedback during surgery, thus affecting clinical decision making. We present our initial experience using high-frequency µUS imaging during spinal procedures. Micro-ultrasound images were obtained in five spinal procedures. Medical rationale for use of µUS was provided for each patient. Surgical procedures were performed using the standard clinical practice with bone removal to facilitate real-time ultrasound imaging of the soft tissue. During surgery, the µUS probe was registered to the pre-operative computed tomography and magnetic resonance images. Images obtained comprised five spinal decompression surgeries (four tumor resections, one cystic synovial mass). Micro-ultrasound images obtained during spine surgery delineated exquisite detailing of the spinal anatomy including white matter and gray matter tracts and nerve roots and allowed accurate assessment of the extent of decompression/tumor resection. In conclusion, tracked µUS enables real-time imaging of the surgical cavity, conferring significant qualitative improvement over conventional ultrasound.

Perspective review on applications of optics in spinal surgery.

Optical technologies may be applied to multiple facets of spinal surgery from diagnostics to intraoperative image guidance to therapeutics. In diagnostics, the current standard remains cross-sectional static imaging. Optical surface scanning tools may have an important role; however, significant work is required to clearly correlate surface metrics to radiographic and clinically relevant spinal anatomy and alignment. In the realm of intraoperative image guidance, optical tracking is widely developed as the current standard of instrument tracking, however remains compromised by line-of-sight issues and more globally cumbersome registration workflows. Surface scanning registration tools are being refined to address concerns over workflow and learning curves, and allow real-time update of tissue deformation; however, the line-of-sight issues plaguing instrument tracking remain to be addressed. In therapeutics, optical applications exist in both visualization, in the form of endoscopes, and ablation, in the form of lasers. Further work is required to extend the feasibility of laser ablation to multiple tissues, including disc, bone, and tumor, in a safe and time-efficient manner. Finally, we postulate some of the short- and long-term opportunities for future growth of optical techniques in the context of spinal surgery. Particular emphasis is placed on intraoperative image guidance, the area of the authors' primary expertise.